My Setup

stevekale · Post by **stevekale** » Mon May 16, 2011 11:33 am

One more question. How critical is the coarse movement on the lateral axis? If one used a Stackshot instead of the M433 translation stage under the camera then forward/backward movement (nearer to or further from the object) could be managed by that and if everything on the object stage is aligned properly then presumably only finer adjustment is needed.

rjlittlefield · Post by **rjlittlefield** » Mon May 16, 2011 11:50 am

stevekale wrote:One more question. How critical is the coarse movement on the lateral axis?

I'm not quite sure what's being asked. But see http://www.photomacrography.net/forum/v ... hp?t=11482 and notice that vertical axis subject positioning is controlled only with one knob on an inexpensive 2-axis macro rail. That approach works fine up to 10X or so on sensor. At 40X it gets pretty twitchy because the total frame height is then only about 1/3 mm. It's still usable, but I have to be very careful when adjusting it.

--Rik

stevekale · Post by **stevekale** » Mon May 16, 2011 12:35 pm

Mark's setup has fine subject position adjustment. He also has coarse camera position adjustment - left, right, forward, back. Forward, back I get (and if one were using a Stackshot you could use that to adjust the start position). But if the camera mount is aligned dead centre with a neutral, middle setting for the subject positioning, surely the fine subject positioning is all that's needed.

( I am questioning the need for 3 in the second photo. Could a Stackshot replace 4, 5, 6 in second photo? I am also assuming that these items are bolted to the granite, otherwise it would defeat the purpose somewhat, and so could be aligned with the subject stage in mid position.)

rjlittlefield · Post by **rjlittlefield** » Mon May 16, 2011 2:21 pm

OK, now I see where you're going.

Yes, item 3 moving the camera sideways could be omitted without much loss. That would limit lateral movement to be the 1/2" slide on the subject mount, plus repositioning the magnetic pin on the top of the subject mount.

Yes, a StackShot could replace items 4, 5, 6, particularly if it were the new longer model with 8" travel instead of only 4". It looks to me that in Marc's setup, there's less than 8" travel on that rail anyway.

--Rik

rjlittlefield · Post by **rjlittlefield** » Mon May 16, 2011 2:39 pm

As long as you're optimizing, one axis of the goniometer could go away also because it's redundant with rotating the camera around the axis of the bellows. That would leave the rotation platform plus the top half of the goniometer to tilt the subject around the other two axes.

--Rik

Craig Gerard · Post by **Craig Gerard** » Wed Apr 04, 2012 7:45 pm

I see item #6 in the second image of this thread to be an important inclusion because a StackShot is difficult to use for 'fine' positioning, it 'jumps' too much in either direction at higher magnifications when attempting to isolate a particular feature or composition of the subject by toggling between the 'Fwd' and 'Back' buttons. The inclusion of the manual translation stage provides a smooth, fine focus, 'hands on' tweak ability.

In reference to the StackShot:

The speed and ramp time are adjustable, so you can set this motion as appropriate for your tastes and equipment.

Could someone expand upon that statement with consideration of high magnifcation viewing? I have yet to play with the 'speed' and 'ramp' time of the StackShot. Does someone have a 'cheat sheet' for such adjustments when using various microscope objectives?

Craig

rjlittlefield · Post by **rjlittlefield** » Wed Apr 04, 2012 9:10 pm

Craig Gerard wrote:a StackShot is difficult to use for 'fine' positioning, it 'jumps' too much in either direction at higher magnifications when attempting to isolate a particular feature or composition of the subject by toggling between the 'Fwd' and 'Back' buttons.

This sounds like the backlash issue caused by play in the screw mechanism of the rail. The FWD and BACK buttons on the controller box and in the Zerene Stacker interface do not attempt to correct for backlash, so there will be a certain amount of dead time when the direction is reversed, followed by sudden movement when the screw re-contacts the nut. If the backlash distance is accurately calibrated for the particular rail, then the focus knobs in the Zerene Stacker GUI can hide almost all of the backlash distance by making relatively long runs of the stepper motor to take up backlash when direction is reversed.

However, there will remain a small amount of twist in the StackShot carriage that occurs when direction is reversed. This twist will affect framing at high magnification. To get accurate framing, you must be sure that the StackShot has been run in the direction that the stack will be taken. This will be true even if you have added a zero-backlash manual stage to provide smooth hands-on tweaking.

--Rik

Craig Gerard · Post by **Craig Gerard** » Thu Apr 05, 2012 1:02 am

This will be true even if you have added a zero-backlash manual stage to provide smooth hands-on tweaking.

Thanks Rik,

Yes, I understand the backlash principle.

Sometimes I prefer to take single exposures or explore a particular area with subtle focus adjustments and don't always use focus stacking, hence my desire for the inclusion of a manual translation element. For an horizontal setup I currently have a Newport 436, it's six inches long and provides 50mm of translation, sitting directly beneath an extended StackShot rail. On my vertical rig I've incorporated a Unifoc 58 for exactly the same reason and have been surprised at just how often I intuitively reach for those manual adjustment dials.

Craig